This invention relates to a camera crane with a two-arm boom swivel-mounted on a support column, whose height can be adjusted if so desired. The first arm has a platform swivel-mounted to receive a camera and, if so desired, a seat for a camera-man and the second arm has a cage swivel-mounted to receive balance weights. A parallel-guide apparatus serves to guide the platform and cage in parallel fashion when the boom is swung out, the parallel-guide apparatus comprising a first control arm running diagonal to the swivel axis of the platform and projecting from the platform, with a first connecting point; a second control arm running diagonal to the swivel axis of the cage and projecting from said cage, with a second connecting point; a guide arm running diagonal to the swivel axis of the boom and projecting from the support column, with a guide connecting point; a first guide rod running between the guide connecting point and the first connecting point, and a second guide rod running between the guide connecting point and the second connecting point.
With camera cranes of this type, the boom arm to which the platform is linked is longer than the boom arm supporting the cage. In selecting cage weights to equalize the weight bearing upon the boom on its platform side, attention must be given to the fact that a correspondingly higher cage weight exerts a torque on the guide arm, by way of the second control arm and the second guide rod, that is greater than the torque exerted on the guide arm by the platform carrying the camera and the camera-man by way of the first control arm and the first guide rod. The practical demand for lengthening the boom arm on the platform side in certain applications cannot be fulfilled without further consideration. This extension would require an increased weight load on the cage, in keeping with the shorter boom arm on the cage side. The torque exerted by the cage on the guide arm by way of the second guide rod, however, can reach an inadmissibly high value relative to that of the torque working against it on the platform side. In actual practice, to safely lengthen the boom arm on the platform side therefore requires that the boom arm on the cage side be correspondingly lengthened. However, the measures necessary to extend the boom arms and thereby to increase the hoist of the camera platform are extremely involved and time-consuming.